Architecture just not delivering a full potential - options?

[Rade]

We have a Generac solar architecture installed on our home. 32 panels, inverter, 18kW battery backup. It works okay... but I just don't believe we are getting the most out of the system.

• When I set the inverter to "Self Supply" and have drawn the batteries down (I do that periodically), during full sun, I can see the panels generating to their fullest potential; 13.2kWh. Beautiful! Batteries get recharged and slowly the residual energy gets fed back to the grid for those glorious Net Credits as the batteries reach capacity.
• But once the batteries are 100% recharged and/or the inverter is set to "Clean Backup" (normal setting), I get no more than 8.6kWh out of our solar panels and the energy being sent back to the grid for net credits is never more than 6.4kWh.

Spoke with our Generac rep, she believes it is a constraint of our inverter, that our solar array is larger than the single inverter can handle.

So we're bantering around different options:

1. Larger inverter - We have limited space in the utility room where the current hub (batteries, inverter, fail-over, etc.) are located. Replacing the current inverter with something that can handle more power sounds good, but... no such beast exists unless we go off product and risk the extended warranties on the remaining parts.
2. Second inverter - Install a second inverter and split the panel load. This may be an easier route given that we have half the panels on the garage and the other half on the house. But either we tear the current system completely down to rewire everything into the tight foot print, or we figure a way to install the second inverter in the garage and use that sub-panel to feed back to the primary panel.

Not obsessing over design and architecture; that will fall into place.

My question: Would the second inverter solve the issue of getting more out of the panels towards the net credits?

Thanks in advance.
Rade

[J.P.M.]

Wasn't this covered in one of your 03/22/25 posts ?

[Rade]

Wasn't this covered in one of your 03/22/25 posts ?

And yes, from the discussion, it appeared to be a clipping issue with the inverter; that we are producing more power than the single inverter can pass back to the grid.

I posed the question to our installer and they suggested that a second inverter might be an option; I just wanted to confirm with the folks here if splitting the panel load between two inverters would address the issue.

[oregon_phil]

It really bugs me when a company of a proprietary closed system says, "she believes it is a constraint of our inverter, that our solar array is larger than the single inverter can handle." The answer is either yes it's the inverter or no it's not the inverter.

Read the attached brochure. You have a 7.7kW inverter. Under perfect conditions, you can only push a maximum 7.7kW back to the grid. The brochure says Maximum recommended DC Power from PV of 10kW (footnote: Additional PV power is permissible if sufficient battery storage capacity is installed). You have 13.2kW which is 1.8 DC/AC ratio. When your batteries are full with full sun, the inverter must be heavily throttling back because you are over the Maximum recommended 10kW PV limit. Some sparkie at the company must have a derating table for the inverter somewhere.

I think you are going to have to work with Generac on potential solutions because you have a closed proprietary system. I would run an ROI on different scenarios to see which one makes the most sense for you. From what I gather from your post, you want to use all of the 13.2kW to the last drop and push excess back to the grid. How does that fit in with having batteries as a house backup?

[Rade]

It really bugs me when a company of a proprietary closed system says, "she believes it is a constraint of our inverter, that our solar array is larger than the single inverter can handle." The answer is either yes it's the inverter or no it's not the inverter.

Read the attached brochure. You have a 7.7kW inverter. Under perfect conditions, you can only push a maximum 7.7kW back to the grid. The brochure says Maximum recommended DC Power from PV of 10kW (footnote: Additional PV power is permissible if sufficient battery storage capacity is installed). You have 13.2kW which is 1.8 DC/AC ratio. When your batteries are full with full sun, the inverter must be heavily throttling back because you are over the Maximum recommended 10kW PV limit. Some sparkie at the company must have a derating table for the inverter somewhere.

I think you are going to have to work with Generac on potential solutions because you have a closed proprietary system. I would run an ROI on different scenarios to see which one makes the most sense for you. From what I gather from your post, you want to use all of the 13.2kW to the last drop and push excess back to the grid. How does that fit in with having batteries as a house backup?

Phil, I'd love to get 7.7kW! Thank you for the brochure. I see where in the material where, YES! We could get up to 10kW of power driven back to the grid. I'm going to send the brochure to our regional tech and ask "Hey... can you 'splain this?"

I always get the best insight from this forum! Thank you!
Rade

[oregon_phil]

For clarification, the brochure implies that you can overpanel maximum recommended PV to 10kW DC for the 7.7kW AC inverter (1.3DC to AC ratio) if you didn't have batteries. The inverter will never push more than 7.7kW back to the grid and it might even be less than this because of AC voltage rise. I don't know what your line voltage is running at. Put together a table of likely scenarios of your system and pose that to Generac to determine the answer.

[Rade]

Phil, I put it back in their lap. I'll see what they come up with. We have 32 panels that can generate 13.2kW of power, plus 18kW of battery backup (currently fully charged). Main service voltage it 240vac. Like I mentioned, the system seems to be throttled to no more than 6.5kW outbound. The building permit has 7.6kW listed as inverter nominal AC power output back to the grid.

I know we got a lot more than 6.5kW at one time; I'll take even one more kW for now. Especially now; the sun it directly overhead for a good portion of the day.

Thanks,
Rade

[azdave]

I don't recall all the prior interconnect details with your grid-tie agreement, but if you haven't done so yet, you should be sure your POCO contract doesn't limit how much you can feed into the grid at any given moment. I am limited to 6kW. I believe 10kW is the max limit in my area before your install is treated as a commercial installation and not residential. Your POCO may not allow back feeding that extra energy when your self-consumption is low, especially when you aren't recharging batteries either.